[CI] Install sccache on XLA build job (pytorch#126117)

XLA build job uses a docker image from XLA, which doesn't have sccache installed.  The XLA build job just builds pytorch, XLA gets built during the test job.  The pytorch build was taking 1+hrs, with a warm cache it takes <30min
Pull Request resolved: pytorch#126117
Approved by: https://github.com/malfet

.ci/pytorch/build.sh

@@ -289,6 +289,9 @@ else
       fi
       WERROR=1 python setup.py bdist_wheel
     else
+      if [[ "$BUILD_ENVIRONMENT" == *xla* ]]; then
+        source .ci/pytorch/install_cache_xla.sh
+      fi
       python setup.py bdist_wheel
     fi
     pip_install_whl "$(echo dist/*.whl)"

.ci/pytorch/install_cache_xla.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+
+# Script for installing sccache on the xla build job, which uses xla's docker
+# image and doesn't have sccache installed on it.  This is mostly copied from
+# .ci/docker/install_cache.sh.  Changes are: removing checks that will always
+# return the same thing, ex checks for for rocm, CUDA, and changing the path
+# where sccache is installed, and not changing /etc/environment.
+
+set -ex
+
+install_binary() {
+  echo "Downloading sccache binary from S3 repo"
+  curl --retry 3 https://s3.amazonaws.com/ossci-linux/sccache -o /tmp/cache/bin/sccache
+}
+
+mkdir -p /tmp/cache/bin
+mkdir -p /tmp/cache/lib
+export PATH="/tmp/cache/bin:$PATH"
+
+install_binary
+chmod a+x /tmp/cache/bin/sccache
+
+function write_sccache_stub() {
+  # Unset LD_PRELOAD for ps because of asan + ps issues
+  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90589
+  # shellcheck disable=SC2086
+  # shellcheck disable=SC2059
+  printf "#!/bin/sh\nif [ \$(env -u LD_PRELOAD ps -p \$PPID -o comm=) != sccache ]; then\n  exec sccache $(which $1) \"\$@\"\nelse\n  exec $(which $1) \"\$@\"\nfi" > "/tmp/cache/bin/$1"
+  chmod a+x "/tmp/cache/bin/$1"
+}
+
+write_sccache_stub cc
+write_sccache_stub c++
+write_sccache_stub gcc
+write_sccache_stub g++
+write_sccache_stub clang
+write_sccache_stub clang++